1. Field of Invention
The present invention relates to a display device, a drive circuit thereof, and a driving method therefor. The invention further relates to electronic equipment that achieve reduced power consumption while restraining degradation in display quality in, for example, device where the switching of pixels is performed by a thin film diode.
2. Description of Related Art
Currently, display units making use of electro-optical changes of liquid crystals are being extensively used with a variety of electronic equipment, such as televisions, and the like, as display devices that replace cathode ray tubes (CRT) by taking advantage of their features, such as thin compact designs and lower power consumption.
The display devices may be roughly divided on the basis of a driving system or the like into an active matrix type in which pixels are driven by switching and a passive matrix type in which pixels are driven without using switching elements. Of these, the active matrix type may be further roughly divided on the basis of the type of switching elements into a type that uses three-terminal switching elements, such as thin film transistors (TFTs), and a type that uses two-terminal type switching elements, such as thin film diodes (TFDs). The two-terminal type switching elements are considered to be advantageous in that a problem of short-circuit among wires does not theoretically occur because of the absence of intersections of wires. Accordingly, a film forming process and a photolithography process can be shortened, and the switching element is suited for achieving lower power consumption.
Meanwhile, in a display device in which pixels are switched by the two-terminal type switching elements, various modes that can lead to degraded display quality exist. However, it is known that such degradation problem of display quality can be solved by using a four-value driving method (½H, 1H inversion) in which the ratio of a period during which two voltages that a data line (segment electrode) may take are applied is lastly halved regardless of a pattern to be displayed.
Especially in portable electronic equipment, such as a PDA (Personal Digital Assistant) and a cellular telephone, that are mainly battery-driven, so that there is a high demand that they consume less power. For this reason, there has been accordingly high demand for lower power consumption in the display devices of portable electronic equipment.
Furthermore, diverse functions, including the reproduction of music, have been added to such a type of portable electronic equipment, and there has even been a demand for reducing the power consumption of the display device even if it is just 1 mW in order to secure electric power applied to such additional functions.
On the other hand, in recent years, display devices have been required to provide higher gray scale display for performing display with more intermediate gray scales in addition to simple monochromic display.